Secondary battery negative electrode slurry, method for preparing the same, secondary battery negative electrode sheet, secondary battery, and use thereof
By adding sulfone solvents to the negative electrode slurry of secondary batteries, the problem of electrode defects during the coating process was solved, the yield of negative electrode sheets and the stability of battery performance were improved, and efficient battery manufacturing was achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- FARASIS TECH (GANZHOU) CO LTD
- Filing Date
- 2022-10-12
- Publication Date
- 2026-07-31
AI Technical Summary
The existing coating process for negative electrode sheets in secondary batteries is prone to problems such as bulging, wrinkling, and cracking at the edges of the electrode sheets, which affects the yield rate. In addition, the existing solvents are prone to decomposition under high temperature conditions, which affects the battery performance.
By using specific sulfone solvents as additives, the surface tension of aqueous solvents is reduced, the wetting effect of active materials and solvents is improved, the dispersion uniformity is enhanced, and the solvent evaporation rate is slowed down during high-temperature and high-speed coating, thus preventing electrode defects.
This improves the yield of negative electrode sheets, ensures battery performance stability, and the sulfone solvent has good thermal stability, which does not affect the battery's electrochemical performance.
Smart Images
Figure CN115579469B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of new energy, and in particular to a secondary battery negative electrode slurry, a method for preparing the secondary battery negative electrode slurry, a negative electrode sheet and a secondary battery prepared using the negative electrode slurry, and their applications. Background Technology
[0002] With the continuous depletion of non-renewable energy sources, carbon dioxide emissions are increasing, and the greenhouse effect is intensifying, leading to a surge in enthusiasm for developing new energy sources. Secondary batteries, due to their advantages such as light weight, high energy density, wide operating voltage range, wide operating temperature range, small size, and long cycle life, have sparked a global research and development boom.
[0003] One of the keys to the successful development and application of secondary batteries lies in the preparation of reversible intercalation and deintercalation negative electrodes. Therefore, research on the fabrication of negative electrodes for secondary batteries is particularly important. As the development and research of secondary batteries become increasingly mature, the requirements for battery energy density are getting higher and higher, and the required coating surface density is getting larger and larger. Existing coating machines and coating methods (including coatings) are prone to causing problems such as bulging, wrinkling, and cracking of electrode edges during coating. Summary of the Invention
[0004] To address the aforementioned technical problems, this invention aims to provide an improved negative electrode slurry for secondary batteries, its preparation method, and negative electrode sheets and secondary batteries prepared using this slurry. The negative electrode slurry and its preparation method of this invention, by adding specific negative electrode additives (e.g., solvent additives) during the slurry preparation process, can reduce the surface tension of aqueous solvents, improve the wetting effect of active materials and solvents, enhance the dispersion uniformity of negative electrode particles in aqueous solutions, slow down the evaporation rate of solvents during high-temperature, high-speed coating, prevent phenomena such as edge bulging, wrinkling, and cracking of the electrode sheet during coating, and improve the yield of the negative electrode sheet. Simultaneously, this negative electrode additive has a stable structure, is not easily hydrolyzed, has good thermal stability, can be used as a solvent or additive in the electrolyte, and its residue in the electrode sheet will not affect the electrochemical performance of the secondary battery.
[0005] Specifically, this invention provides:
[0006] 1. A secondary battery negative electrode slurry, comprising a solvent, a negative electrode active material, a conductive agent, a binder, a thickener, and additives, wherein the additives are any one or more compounds of formula (1) and formula (2):
[0007]
[0008] R1 and R2 each independently represent a C1-C12 hydrocarbon group, a C1-C12 alkoxy group, a C6-C12 aromatic group, or a C7-C12 aralkyl group, wherein the C1-C12 hydrocarbon group, C1-C12 alkoxy group, C6-C12 aromatic group, or C7-C12 aralkyl group is optionally substituted by at least one substituent selected from C1-C12 alkyl or C1-C12 alkoxy groups, and
[0009] R3 and R4 each independently represent a C1-C12 alkylene group or a C1-C12 alkoxy group, wherein the C1-C12 alkylene group and the C1-C12 alkoxy group are optionally substituted by at least one substituent selected from C1-C12 alkyl or C1-C12 alkoxy groups.
[0010] 2. A method for preparing a secondary battery negative electrode slurry, comprising the following steps:
[0011] Provides a negative electrode base component, which includes a solvent, a negative electrode active material, a conductive agent, a binder, and a thickener; and
[0012] The additives are mixed with the aforementioned negative electrode base components to obtain a secondary battery negative electrode slurry.
[0013] The additive is any one or more of the compounds shown in formula (1) and formula (2):
[0014]
[0015] Wherein R1 and R2 independently represent a C1-C12 hydrocarbon group, a C1-C12 alkoxy group, a C6-C12 aromatic group, or a C7-C12 aralkyl group, wherein the C1-C12 hydrocarbon group, C1-C12 alkoxy group, C6-C12 aromatic group, or C7-C12 aralkyl group is optionally substituted by at least one substituent selected from C1-C12 alkyl or C1-C12 alkoxy groups, and
[0016] R3 and R4 each independently represent a C1-C12 alkylene group or a C1-C12 alkoxy group, wherein the C1-C12 alkylene group and the C1-C12 alkoxy group are optionally substituted by at least one substituent selected from C1-C12 alkyl or C1-C12 alkoxy groups.
[0017] 3. A secondary battery negative electrode sheet, comprising a negative electrode current collector and a negative electrode film disposed on at least one surface of the negative electrode current collector, wherein the negative electrode film comprises the aforementioned secondary battery negative electrode slurry.
[0018] 4. A secondary battery, comprising: a positive electrode, a negative electrode, a separator, an electrolyte, and a packaging film, wherein the negative electrode is the aforementioned negative electrode.
[0019] 5. Application of the above-mentioned secondary batteries in new energy vehicles.
[0020] This invention has one of the following beneficial effects:
[0021] (1) The negative electrode additive can reduce the surface tension of the aqueous solvent, improve the wetting effect of the active material and the solvent, improve the dispersion uniformity of the negative electrode particles in the aqueous solution, slow down the evaporation rate of the solvent during high-temperature and high-speed coating, prevent the electrode edge bulging, wrinkling and cracking during coating, and improve the yield of the negative electrode.
[0022] (2) The negative electrode additive has a stable structure, is not prone to hydrolysis, has good thermal stability, and can be used as a solvent or additive for electrolyte. It will not affect the electrochemical performance of secondary batteries if it remains in the electrode. Brief description of the attached figures
[0023] Figure 1 The comparison of cycle performance in the performance test of the secondary batteries prepared in Example 1 of the present invention and Comparative Examples 1-2 is shown. Detailed Implementation
[0024] Before providing a more detailed description of this disclosure, it should be understood that the scope of this disclosure is not limited to the specific embodiments described, and therefore, the embodiments of this disclosure can certainly be varied. It should also be understood that since the scope of this disclosure is defined only by the appended claims, the terminology used herein is for descriptive purposes only and not intended to be limiting.
[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by a person skilled in the art.
[0026] All publications and patents mentioned in this specification are incorporated herein by reference as if each publication or patent were specifically cited separately and incorporated herein by reference for the purpose of disclosing and describing methods and / or structures relating to the cited publications.
[0027] Having read the disclosure of this application, it will be apparent to those skilled in the art that each embodiment described and illustrated herein has separate components and features that can be readily separated from each other or combined with features of any of the other several embodiments without departing from the scope and spirit of the invention. Any method described may be implemented in the chronological order of events described or in any other logically feasible order.
[0028] It must be noted that, in this specification and the appended claims, unless the context clearly specifies otherwise, the singular forms “a,” “an,” “the,” and the unspecified number of terms cover cases with multiple referents.
[0029] Unless otherwise specified, all figures used in this disclosure to represent quantities and physical properties should be understood to be modified by the term "about" in all cases. Therefore, unless stated to the contrary, the numerical parameters listed in the specification and claims are approximations, and those skilled in the art can appropriately modify these approximations to obtain the desired properties using the teachings disclosed herein. No attempt is made to limit the application of the doctrine of equivalence of the claims, and each numerical parameter is at least considered to be obtained based on the reported significant figures and by conventional rounding methods. Furthermore, a numerical range represented by an end value includes that end value, as well as all subranges and values within that range (e.g., 30-40 includes 30, 31, 31.5, 32.3, 35-40, etc.). In this article, the numerical values in the form X±Y represent the range of values from XY to X+Y, which also includes the endpoints XY, X+Y, and all subranges and values within that range (e.g., 30±5 includes 25, 26, 27, 28, 29.5, 30.8, 31-33, 31-35, 35, etc.).
[0030] Various additives exist to improve the performance of the negative electrode in secondary batteries. For example, polar ethylene carbonate can be added to aqueous negative electrode slurry to effectively improve coating cracking of aqueous negative electrode sheets. However, this method has very limited effect on reducing solvent surface tension, and ethylene carbonate is prone to hydrolysis at high temperatures, with the resulting ethylene glycol easily degrading the high-voltage performance of the battery cell.
[0031] The solvent N-methylpyrrolidone can also be added to the negative electrode slurry. This method provides a secondary battery negative electrode slurry with high safety performance that can automatically block the heat generation reaction when abnormal heat is generated inside lithium ions. Its negative electrode active material is 80 parts of spherical graphite, the conductive agent is 0.5 parts of carbon nanotubes, the solvent is N-methylpyrrolidone, and the negative electrode binder is 1.5 parts. The amount of N-methylpyrrolidone solvent required for the negative electrode slurry prepared by this method is too large, and NMP will catalyze ring opening under alkaline conditions, resulting in poor chemical stability. The electrode heating and drying process cannot completely remove NMP, and the residual NMP is adsorbed on the graphite surface, affecting the long cycle performance of the battery.
[0032] This invention provides an improved negative electrode slurry for secondary batteries, in which a specific sulfone solvent is added as an additive to the basic components of the negative electrode. Sulfone solvents are aprotic, strongly polar, water-soluble organic sulfur solvents with advantages such as good thermal stability, strong solubility, high selectivity, low corrosiveness to equipment, and low toxicity to humans. Compared with solvents such as NMP and ethylene carbonate, they do not undergo decomposition reactions during the formulation, coating, and drying processes. Furthermore, ethylene carbonate has a high melting point, requiring heating to dissolve, increasing manufacturing and labor costs. NMP is highly hygroscopic, and water absorption can affect the later performance of the battery; therefore, environmental humidity must be strictly controlled during battery manufacturing, increasing production costs. Sulfone solvents can reduce manufacturing costs. Moreover, sulfone solvents can be used as solvents or additives in the electrolyte, and their residue in the electrode does not affect the electrochemical performance of the secondary battery.
[0033] In one aspect, the present invention provides a secondary battery negative electrode slurry comprising a solvent, a negative electrode active material, a conductive agent, a binder, a thickener, and additives.
[0034] The additive can be any one or more of the compounds shown in formula (1) and formula (2):
[0035]
[0036] Wherein R1 and R2 independently represent a C1-C12 hydrocarbon group, a C1-C12 alkoxy group, a C6-C12 aromatic group, or a C7-C12 aralkyl group, wherein the C1-C12 hydrocarbon group, C1-C12 alkoxy group, C6-C12 aromatic group, or C7-C12 aralkyl group is optionally substituted by at least one substituent selected from C1-C12 alkyl or C1-C12 alkoxy groups, and
[0037] R3 and R4 each independently represent a C1-C12 alkylene group or a C1-C12 alkoxy group, wherein the C1-C12 alkylene group and the C1-C12 alkoxy group are optionally substituted by at least one substituent selected from C1-C12 alkyl or C1-C12 alkoxy groups.
[0038] In this document, C1-C12 hydrocarbon groups refer to organic groups composed of carbon and hydrogen elements having 1-12 carbon atoms, preferably 1-6 carbon atoms, including but not limited to C1-C12 alkyl, C2-C12 alkynyl or C2-C12 alkenyl, preferably C1-C6 alkyl, C2-C6 alkynyl and C2-C6 alkenyl, and more preferably methyl, ethyl, n-butyl, isobutyl, n-propyl, isopropyl, vinyl, propenyl, etc.
[0039] In this document, C1-C12 alkoxy refers to an alkyl group having 1-12, preferably 1-6, carbon atoms interspersed with oxygen atoms, including but not limited to methoxy, ethoxy, propoxy, butoxy, etc.
[0040] In this article, C6-C12 aromatic groups refer to aromatic hydrocarbon organic groups having 6-12, preferably 6-8, carbon atoms, including but not limited to phenyl, naphthyl, etc.
[0041] In this article, C7-C12 aralkyl refers to an aromatic group having 7-12 carbon atoms and attached to an alkyl group, including but not limited to benzyl, phenethyl, naphthylmethyl, naphthylethyl, etc.
[0042] In this document, C1-C12 alkylene refers to a divalent hydrocarbon organic group having 1-12 carbon atoms, preferably 1-6 carbon atoms, with two connection points, including but not limited to C1-C12 alkylene, C2-C12 yntylide, or C2-C12 alkenylene, preferably C1-C6 alkylene, C2-C6 yntylide, and C2-C6 alkenylene, and more preferably methylene, ethylene, n-butylene, isobutylene, n-propylene, isopropylene, vinylene, propenylene, etc.
[0043] In this article, C1-C12 alkeneoxy refers to a divalent oxygen-containing organic group with 1-12, preferably 1-6, carbon atoms interspersed with oxygen atoms, having two connection points, including but not limited to methoxy, ethoxy, propoxy, and butoxy.
[0044] Each of the above groups may optionally be replaced by at least one substituent selected from C1-C12 alkyl or C1-C12 alkoxy groups.
[0045] According to one embodiment of the present invention, all components in the negative electrode of the secondary battery, except for the solvent and additives, are solutes.
[0046] The solute, by mass percentage, comprises 92.0%–95.0% negative electrode active material, 0.5%–1.5% conductive agent, 1.0%–1.5% thickener, 2.0%–2.3% binder, and 0.2%–1.5% additives.
[0047] Optionally, the negative electrode active material may be selected from at least one of artificial graphite, natural graphite, mesophase carbon microspheres, silicon-carbon, silicon-oxygen, and hard carbon.
[0048] Optionally, the conductive agent may be selected from at least one of carbon black, carbon nanotubes, graphene, and conductive fibers.
[0049] Optionally, the thickener may be selected from at least one of sodium carboxymethyl cellulose and lithium carboxymethyl cellulose.
[0050] Optionally, the adhesive may be selected from at least one of styrene-butadiene rubber and polyacrylic acid.
[0051] Preferably, the compound shown in formula (1) may be selected from at least one of dimethyl sulfone, diethyl sulfone, ethyl methyl sulfone, n-butyl sulfone, methoxyethyl methyl sulfone, ethyl methoxyethyl sulfone, ethyl methoxyethoxyethyl sulfone, dibutyl sulfone, methyl vinyl sulfone, ethyl vinyl sulfone, benzyl sulfone, benzyl phenyl sulfone and ethylbutadiene disulfone.
[0052] The compound shown in formula (2) may be selected from at least one of sulfolane, sulfolane and 3-methylsulfolane, preferably sulfolane.
[0053] In another aspect, the present invention provides a method for preparing a secondary battery negative electrode slurry, comprising the following steps: providing a negative electrode base component, the negative electrode base component comprising a solvent, a negative electrode active material, a conductive agent, a binder, and a thickener; and mixing an additive with the negative electrode base component to obtain the secondary battery negative electrode slurry.
[0054] The additive is any one or more of the compounds shown in formula (1) and formula (2):
[0055]
[0056] R1 and R2 each independently represent a C1-C12 hydrocarbon group, a C1-C12 alkoxy group, a C6-C12 aromatic group, or a C7-C12 aralkyl group, wherein the C1-C12 hydrocarbon group, C1-C12 alkoxy group, C6-C12 aromatic group, or C7-C12 aralkyl group is optionally substituted by at least one substituent selected from C1-C12 alkyl or C1-C12 alkoxy groups, and
[0057] R3 and R4 each independently represent a C1-C12 alkylene group or a C1-C12 alkoxy group, wherein the C1-C12 alkylene group and the C1-C12 alkoxy group are optionally substituted by at least one substituent selected from C1-C12 alkyl or C1-C12 alkoxy groups.
[0058] In this document, the solvent can be any solvent used in the art for preparing electrode materials, provided it differs from the additive. Examples of solvents include, but are not limited to, deionized water, dimethyl sulfoxide, and N-methylpyrrolidone.
[0059] In one implementation, the step of providing the negative electrode base component includes:
[0060] S1: Mix 43-47 parts of the negative electrode active material, 0.4-0.9 parts of the conductive agent and 0.2-0.5 parts of the thickener;
[0061] S2: Add 29-32 parts of solvent to the mixture from step S1, mix, and then add 0.5-0.9 parts of thickener;
[0062] S3: Add 18-20 parts of solvent to the mixing system of step S2, mix, and then add 0.4-0.8 parts of the binder to obtain the basic components of the negative electrode.
[0063] Preferably, the method further includes the following step: S4: adding 0.4-0.8 parts of additive to the mixing system of step S3 to obtain the negative electrode slurry.
[0064] Preferably, the method for preparing the negative electrode slurry of the present invention is as follows:
[0065] S1: Mix 43-47 parts of the negative electrode active material, 0.4-0.9 parts of the conductive agent, and 0.2-0.5 parts of the thickener until homogeneous;
[0066] S2: Add 29-32 parts of solvent to the mixture in step S1, mix and stir evenly, then add 0.5-0.9 parts of thickener, and continue to stir and mix evenly;
[0067] S3: Add 18-20 parts of solvent to the mixture in step S2, mix and stir evenly, then add 0.4-0.8 parts of binder, and continue to stir and mix evenly;
[0068] S4: Add 0.4-0.8 parts of additive to the mixing system of step S3, mix and stir evenly, then add solvent to adjust the viscosity (slurry viscosity is 5000-8000 mPa.s), continue to stir and mix evenly to obtain the negative electrode slurry.
[0069] In a third aspect, the present invention provides a secondary battery negative electrode sheet, comprising a negative electrode current collector and a negative electrode film disposed on at least one surface of the negative electrode current collector, the negative electrode film comprising the secondary battery negative electrode slurry as described above.
[0070] In a fourth aspect, the present invention also provides a method for preparing a secondary battery negative electrode sheet, comprising the following steps: providing a secondary battery negative electrode slurry as described above and coating the secondary battery negative electrode slurry onto a negative electrode current collector.
[0071] Preferably, the method for preparing the negative electrode sheet of the present invention is as follows:
[0072] (1) The negative electrode slurry prepared according to the preparation method of the present invention is subjected to temperature, viscosity, solid content, fineness, vacuum degassing (preferably vacuum degree ≤90KPa during vacuuming), sieving (preferably sieve mesh number: 150 mesh) and discharge treatment in sequence;
[0073] (2) Coat the negative electrode slurry (preferably by extrusion coating) onto the negative electrode current collector, and then roll, dry and punch to obtain the negative electrode sheet.
[0074] The present invention also provides a negative electrode sheet prepared by the above method.
[0075] In a fifth aspect, the present invention provides a secondary battery comprising: a positive electrode, a negative electrode, a separator, an electrolyte, and a packaging film, wherein the negative electrode is the aforementioned secondary battery negative electrode.
[0076] Optionally, the secondary battery may also include a positive electrode tab, a separator, a negative electrode tab, and an aluminum-plastic film.
[0077] Optionally, the positive electrode sheet comprises a positive electrode active material, and the positive electrode active material is selected from any one of lithium iron phosphate, nickel cobalt manganese ternary, nickel cobalt aluminum ternary, lithium cobalt oxide, lithium manganese phosphate, lithium manganese iron phosphate, transition metal layered sodium oxide, NaMFe(CN)6, and lithium-rich manganese-based materials.
[0078] In a sixth aspect, the present invention also provides an application of a secondary battery in a new energy vehicle, wherein the secondary battery is the aforementioned secondary battery.
[0079] The technical solution of the present invention will be further described below with reference to examples. The examples described below are only some embodiments of the present invention, and the scope of the present invention is not limited thereto.
[0080] Example 1
[0081] Preparation of negative electrode slurry (with additive sulfolane):
[0082] S1: Add 9996g of active material graphite, 105g of conductive agent SP (conductive carbon black) and 63g of thickener sodium carboxymethyl cellulose to a 15L mixing tank, set the general speed to 20±2rpm and the rotation speed to 1707±50rpm, and stir for 5min to obtain a mixed dry powder.
[0083] S2: Add 6230g of deionized water, set the speed to 15±2 rpm, stir for 40 minutes, then add 95g of thickener sodium carboxymethyl cellulose, set the speed to 15±2 rpm, and stir for 5 minutes.
[0084] S3: Add 3908g of deionized water, set the rotation speed to 25±2rpm and the rotation speed to 2133±50rpm, stir for 60min, then add 65g of additive sulfolane, set the rotation speed to 25±2rpm and the rotation speed to 1707±50rpm, stir for 5min.
[0085] S4: Add 242g of styrene-butadiene rubber binder, set the rotation speed to 25±2 rpm and the rotation speed to 1707±50 rpm, stir for 30 minutes, then add an appropriate amount of deionized water, set the rotation speed to 25±2 rpm and the rotation speed to 1707±50 rpm, stir for 60 minutes, and then evacuate for 30 minutes with a vacuum degree ≤-90KPa to obtain a negative electrode slurry with a viscosity of 5881mPa.s. The viscosity of the slurry was tested using a digital viscometer.
[0086] Example 2
[0087] Preparation of negative electrode slurry (with additive sulfolane):
[0088] S1: Add 9996g of active material graphite, 105g of conductive agent SP (conductive carbon black) and 63g of thickener sodium carboxymethyl cellulose to a 15L mixing tank, set the general speed to 20±2rpm and the rotation speed to 1707±50rpm, and stir for 5min to obtain a mixed dry powder.
[0089] S2: Add 6230g of deionized water, set the speed to 15±2 rpm, stir for 40 minutes, then add 95g of thickener sodium carboxymethyl cellulose, set the speed to 15±2 rpm, and stir for 5 minutes.
[0090] S3: Add 3908g of deionized water, set the rotation speed to 25±2rpm and the rotation speed to 2133±50rpm, stir for 60min, then add 85g of additive sulfolane, set the rotation speed to 25±2rpm and the rotation speed to 1707±50rpm, stir for 5min.
[0091] S4: Add 242g of styrene-butadiene rubber binder, set the rotation speed to 25±2 rpm and the rotation speed to 1707±50 rpm, stir for 30 minutes, then add an appropriate amount of deionized water, set the rotation speed to 25±2 rpm and the rotation speed to 1707±50 rpm, stir for 60 minutes, and then evacuate for 30 minutes with a vacuum degree ≤-90KPa to obtain a negative electrode slurry with a viscosity of 6002mPa.s. The viscosity of the slurry is tested using a digital viscometer.
[0092] Example 3
[0093] Preparation of negative electrode slurry (with additive sulfolane):
[0094] S1: Add 9996g of active material graphite, 105g of conductive agent SP (conductive carbon black) and 63g of thickener sodium carboxymethyl cellulose to a 15L mixing tank, set the general speed to 20±2rpm and the rotation speed to 1707±50rpm, and stir for 5min to obtain a mixed dry powder.
[0095] S2: Add 6230g of deionized water, set the speed to 15±2 rpm, stir for 40 minutes, then add 95g of thickener sodium carboxymethyl cellulose, set the speed to 15±2 rpm, and stir for 5 minutes.
[0096] S3: Add 3908g of deionized water, set the rotation speed to 25±2rpm and the rotation speed to 2133±50rpm, stir for 60min, then add 110g of additive sulfolane, set the rotation speed to 25±2rpm and the rotation speed to 1707±50rpm, stir for 5min.
[0097] S4: Add 242g of styrene-butadiene rubber binder, set the rotation speed to 25±2 rpm and the rotation speed to 1707±50 rpm, stir for 30 minutes, then add an appropriate amount of deionized water, set the rotation speed to 25±2 rpm and the rotation speed to 1707±50 rpm, stir for 60 minutes, and then evacuate for 30 minutes with a vacuum degree ≤-90KPa to obtain a negative electrode slurry with a viscosity of 5746mPa.s. The viscosity of the slurry was tested using a digital viscometer.
[0098] Example 4
[0099] Preparation of negative electrode slurry (with dimethyl sulfone additive):
[0100] S1: Add 9996g of active material graphite, 105g of conductive agent SP (conductive carbon black) and 63g of thickener sodium carboxymethyl cellulose to a 15L mixing tank, set the general speed to 20±2rpm and the rotation speed to 1707±50rpm, and stir for 5min to obtain a mixed dry powder.
[0101] S2: Add 6230g of deionized water, set the speed to 15±2 rpm, stir for 40 minutes, then add 95g of thickener sodium carboxymethyl cellulose, set the speed to 15±2 rpm, and stir for 5 minutes.
[0102] S3: Add 3908g of deionized water, set the rotation speed to 25±2rpm and the rotation speed to 2133±50rpm, stir for 60min, then add 65g of additive dimethyl sulfone, set the rotation speed to 25±2rpm and the rotation speed to 1707±50rpm, stir for 5min.
[0103] S4: Add 242g of styrene-butadiene rubber binder, set the rotation speed to 25±2 rpm and the rotation speed to 1707±50 rpm, stir for 30 minutes, then add an appropriate amount of deionized water, set the rotation speed to 25±2 rpm and the rotation speed to 1707±50 rpm, stir for 60 minutes, and then evacuate for 30 minutes with a vacuum degree ≤-90KPa to obtain a negative electrode slurry with a viscosity of 5567mPa.s. The viscosity of the slurry was tested using a digital viscometer.
[0104] Example 5
[0105] Preparation of negative electrode slurry (with benzyl sulfone additive):
[0106] S1: Add 9996g of active material graphite, 105g of conductive agent SP (conductive carbon black) and 63g of thickener sodium carboxymethyl cellulose to a 15L mixing tank, set the general speed to 20±2rpm and the rotation speed to 1707±50rpm, and stir for 5min to obtain a mixed dry powder.
[0107] S2: Add 6230g of deionized water, set the speed to 15±2 rpm, stir for 40 minutes, then add 95g of thickener sodium carboxymethyl cellulose, set the speed to 15±2 rpm, and stir for 5 minutes.
[0108] S3: Add 3908g of deionized water, set the rotation speed to 25±2rpm and the rotation speed to 2133±50rpm, stir for 60min, then add 65g of additive benzyl sulfone, set the rotation speed to 25±2rpm and the rotation speed to 1707±50rpm, stir for 5min.
[0109] S4: Add 242g of styrene-butadiene rubber binder, set the rotation speed to 25±2 rpm and the rotation speed to 1707±50 rpm, stir for 30 minutes, then add an appropriate amount of deionized water, set the rotation speed to 25±2 rpm and the rotation speed to 1707±50 rpm, stir for 60 minutes, and then evacuate for 30 minutes with a vacuum degree ≤-90KPa to obtain a negative electrode slurry with a viscosity of 6159mPa.s. The viscosity of the slurry was tested using a digital viscometer.
[0110] Example 6
[0111] Preparation of negative electrode slurry (with additive methoxyethyl methyl sulfone):
[0112] S1: Add 9996g of active material graphite, 105g of conductive agent SP (conductive carbon black) and 63g of thickener sodium carboxymethyl cellulose to a 15L mixing tank, set the general speed to 20±2rpm and the rotation speed to 1707±50rpm, and stir for 5min to obtain a mixed dry powder.
[0113] S2: Add 6230g of deionized water, set the speed to 15±2 rpm, stir for 40 minutes, then add 95g of thickener sodium carboxymethyl cellulose, set the speed to 15±2 rpm, and stir for 5 minutes.
[0114] S3: Add 3908g of deionized water, set the rotation speed to 25±2 rpm and the rotation speed to 2133±50 rpm, stir for 60 minutes, then add 65g of additive methoxyethyl methyl sulfone, set the rotation speed to 25±2 rpm and the rotation speed to 1707±50 rpm, stir for 5 minutes.
[0115] S4: Add 242g of styrene-butadiene rubber binder, set the rotation speed to 25±2 rpm and the rotation speed to 1707±50 rpm, stir for 30 minutes, then add an appropriate amount of deionized water, set the rotation speed to 25±2 rpm and the rotation speed to 1707±50 rpm, stir for 60 minutes, and then evacuate for 30 minutes with a vacuum degree ≤-90KPa to obtain a negative electrode slurry with a viscosity of 6382mPa.s. The viscosity of the slurry was tested using a digital viscometer.
[0116] Example 7
[0117] Preparation of negative electrode slurry (with additives sulfolane and dimethyl sulfone):
[0118] S1: Add 9996g of active material graphite, 105g of conductive agent SP (conductive carbon black) and 63g of thickener sodium carboxymethyl cellulose to a 15L mixing tank, set the general speed to 20±2rpm and the rotation speed to 1707±50rpm, and stir for 5min to obtain a mixed dry powder.
[0119] S2: Add 6230g of deionized water, set the speed to 15±2 rpm, stir for 40 minutes, then add 95g of thickener sodium carboxymethyl cellulose, set the speed to 15±2 rpm, and stir for 5 minutes.
[0120] S3: Add 3908g of deionized water, set the rotation speed to 25±2rpm and the rotation speed to 2133±50rpm, stir for 60min, then add 35g of additive sulfolane and 30g of additive dimethyl sulfone, set the rotation speed to 25±2rpm and the rotation speed to 1707±50rpm, stir for 5min.
[0121] S4: Add 242g of styrene-butadiene rubber binder, set the rotation speed to 25±2 rpm and the rotation speed to 1707±50 rpm, stir for 30 minutes, then add an appropriate amount of deionized water, set the rotation speed to 25±2 rpm and the rotation speed to 1707±50 rpm, stir for 60 minutes, and then evacuate for 30 minutes with a vacuum degree ≤-90KPa to obtain a negative electrode slurry with a viscosity of 5943mPa.s. The viscosity of the slurry was tested using a digital viscometer.
[0122] Comparative Example 1
[0123] Preparation of negative electrode slurry (without additives):
[0124] S1: Add 9996g of active material graphite, 105g of conductive agent SP (conductive carbon black) and 63g of thickener sodium carboxymethyl cellulose to a 15L mixing tank, set the general speed to 20±2rpm and the rotation speed to 1707±50rpm, and stir for 5min to obtain a mixed dry powder.
[0125] S2: Add 6230g of deionized water, set the speed to 15±2 rpm, stir for 40 minutes, then add 95g of thickener sodium carboxymethyl cellulose, set the speed to 15±2 rpm, and stir for 5 minutes.
[0126] S3: Add 3908g of deionized water, set the rotation speed to 25±2rpm and the rotation speed to 2133±50rpm, and stir for 60min;
[0127] S4: Add 242g of styrene-butadiene rubber binder, set the rotation speed to 25±2 rpm and the rotation speed to 1707±50 rpm, stir for 30 minutes, then add an appropriate amount of deionized water, set the rotation speed to 25±2 rpm and the rotation speed to 1707±50 rpm, stir for 60 minutes, and then evacuate for 30 minutes with a vacuum degree ≤-90KPa to obtain a negative electrode slurry with a viscosity of 5276mPa.s. The viscosity of the slurry was tested using a digital viscometer.
[0128] Comparative Example 2
[0129] Preparation of negative electrode slurry (with N-methylpyrrolidone additive):
[0130] S1: Add 9996g of active material graphite, 105g of conductive agent SP (conductive carbon black) and 63g of thickener sodium carboxymethyl cellulose to a 15L mixing tank, set the general speed to 20±2rpm and the rotation speed to 1707±50rpm, and stir for 5min to obtain a mixed dry powder.
[0131] S2: Add 6230g of deionized water, set the speed to 15±2 rpm, stir for 40 minutes, then add 95g of thickener sodium carboxymethyl cellulose, set the speed to 15±2 rpm, and stir for 5 minutes.
[0132] S3: Add 3908g of deionized water, set the rotation speed to 25±2rpm and the rotation speed to 2133±50rpm, stir for 60min, then add 110g of microelectronic grade NMP, set the rotation speed to 25±2rpm and the rotation speed to 1707±50rpm, stir for 5min.
[0133] S4: Add 242g of styrene-butadiene rubber binder, set the rotation speed to 25±2 rpm and the rotation speed to 1707±50 rpm, stir for 30 minutes, then add an appropriate amount of deionized water, set the rotation speed to 25±2 rpm and the rotation speed to 1707±50 rpm, stir for 60 minutes, and then vacuum for 30 minutes with a vacuum degree ≤-90KPa to obtain a negative electrode slurry with a viscosity of 5817mPa.s. The viscosity of the slurry was tested using a digital viscometer.
[0134] Comparative Example 3
[0135] Preparation of negative electrode slurry (with N-methylpyrrolidone additive):
[0136] S1: Add 9996g of active material graphite, 105g of conductive agent SP (conductive carbon black) and 63g of thickener sodium carboxymethyl cellulose to a 15L mixing tank, set the general speed to 20±2rpm and the rotation speed to 1707±50rpm, and stir for 5min to obtain a mixed dry powder.
[0137] S2: Add 6230g of deionized water, set the speed to 15±2 rpm, stir for 40 minutes, then add 95g of thickener sodium carboxymethyl cellulose, set the speed to 15±2 rpm, and stir for 5 minutes.
[0138] S3: Add 3908g of deionized water, set the rotation speed to 25±2rpm and the rotation speed to 2133±50rpm, stir for 60min, then add 200g of microelectronic grade NMP, set the rotation speed to 25±2rpm and the rotation speed to 1707±50rpm, stir for 5min.
[0139] S4: Add 242g of styrene-butadiene rubber binder, set the rotation speed to 25±2 rpm and the rotation speed to 1707±50 rpm, stir for 30 minutes, then add an appropriate amount of deionized water, set the rotation speed to 25±2 rpm and the rotation speed to 1707±50 rpm, stir for 60 minutes, and then vacuum for 30 minutes with a vacuum degree ≤-90KPa to obtain a negative electrode slurry with a viscosity of 6054mPa.s. The viscosity of the slurry was tested using a digital viscometer.
[0140] Comparative Example 4
[0141] Preparation of negative electrode slurry (with dimethyl sulfoxide additive):
[0142] S1: Add 9996g of active material graphite, 105g of conductive agent SP (conductive carbon black) and 63g of thickener sodium carboxymethyl cellulose to a 15L mixing tank, set the general speed to 20±2rpm and the rotation speed to 1707±50rpm, and stir for 5min to obtain a mixed dry powder.
[0143] S2: Add 6230g of deionized water, set the speed to 15±2 rpm, stir for 40 minutes, then add 95g of thickener sodium carboxymethyl cellulose, set the speed to 15±2 rpm, and stir for 5 minutes.
[0144] S3: Add 3908g of deionized water, set the rotation speed to 25±2rpm and the rotation speed to 2133±50rpm, stir for 60min, then add 65g of additive dimethyl sulfoxide, set the rotation speed to 25±2rpm and the rotation speed to 1707±50rpm, stir for 5min.
[0145] S4: Add 242g of styrene-butadiene rubber binder, set the rotation speed to 25±2 rpm and the rotation speed to 1707±50 rpm, stir for 30 minutes, then add an appropriate amount of deionized water, set the rotation speed to 25±2 rpm and the rotation speed to 1707±50 rpm, stir for 60 minutes, and then evacuate for 30 minutes with a vacuum degree ≤-90KPa to obtain a negative electrode slurry with a viscosity of 6122mPa.s. The viscosity of the slurry was tested using a digital viscometer.
[0146] Test Example 1
[0147] Methods for detecting cracks and wrinkles:
[0148] S1: Take the slurry prepared in each example and comparative example, and apply it to a 6μm thick copper foil using an extrusion coating method. After coating, visually inspect and pick out the cracked and wrinkled electrodes.
[0149] S2: Count the number of cracked and wrinkled electrode sheets and the number of good electrode sheets, and calculate the electrode sheet yield rate;
[0150] S3: Summarize and compare the yield data of each embodiment with the comparative embodiment.
[0151] Methods for detecting bulges:
[0152] S1: Take samples of the negative electrode sheets prepared in each example and comparative example;
[0153] S2: Measure the thickness change of the electrode in the transverse direction (perpendicular to the coating direction) using a micrometer. If the thickness of the electrode increases significantly, it indicates that the electrode has bulged.
[0154] S3: Statistically determine the location and number of bulges, and compare the location and frequency of bulges in each embodiment and comparative example.
[0155] The test results are shown in Table 1 below.
[0156] Table 1
[0157] example Cracks in the coating of the negative electrode Example 1 No cracking, no bulging. Example 2 No cracking, no bulging. Example 3 No cracking, no bulging. Example 4 No cracking, no bulging. Example 5 No cracking, no bulging. Example 6 No cracking, no bulging. Example 7 No cracking, no bulging. Comparative Example 1 Cracking, numerous electrode edge bulges Comparative Example 2 Partial cracking, and a small number of electrode bulges. Comparative Example 3 No cracking, no bulging. Comparative Example 4 No cracking, but a small number of electrode edges show bulging.
[0158] As can be seen from Table 1, the addition of sulfone compounds to the negative electrode slurry of secondary batteries in this invention can effectively improve the edge bulging, wrinkling and cracking phenomena during the coating of negative electrode sheets.
[0159] Test Example 2
[0160] The negative electrode slurries of Examples 1-7 and Comparative Examples 1-4 were coated onto a 6μm thick copper foil negative electrode current collector, and then rolled, dried, and stamped to obtain negative electrode sheets.
[0161] Using nickel-cobalt-manganese ternary cathode active material as the cathode material, it is dissolved in a solvent with conductive agent (carbon black) and binder (carbon nanotubes) at a mass fraction ratio of 94:3:3. The mixture is mixed evenly with a solid content of 68% to obtain a cathode slurry. The cathode slurry is coated on a 13μm thick aluminum foil cathode current collector, and then rolled, dried, and stamped to obtain a cathode sheet.
[0162] The above-mentioned negative electrode, positive electrode and separator are stacked and packaged in an aluminum-plastic film. Then, an electrolyte (electrolyte formula: lithium hexafluorophosphate 1mol / L, ethylene carbonate: methyl ethyl carbonate = 3:7) is injected into it. Activation, formation, aging and capacity testing are carried out in sequence to obtain a 1.8Ah small soft-pack battery cell.
[0163] Then, the cell capacity, internal resistance, and initial charge / discharge efficiency of the small pouch cells prepared in each embodiment and comparative example were tested. The test standards are shown in Table 2.
[0164] Table 2
[0165]
[0166] The test results are shown in Table 2 below.
[0167] Table 2
[0168] The data (average value) for each embodiment and comparative example were prepared into 30 small soft packages.
[0169]
[0170] As can be seen from the results in Table 2, the embodiments of the present invention that add sulfone compounds to the negative electrode slurry of secondary batteries show no significant difference in cell capacity, DC internal resistance, and first-efficiency performance compared with the corresponding comparative examples.
[0171] Figure 1 The cycle performance of the secondary batteries prepared in the embodiments and comparative examples of the present invention is compared. It can be seen from the cycle graph that the additives described in the present invention have no deteriorating effect on the cycle performance of the secondary batteries, while NMP (N-methylpyrrolidone) deteriorates the cycle performance of the secondary batteries.
Claims
1. A negative electrode slurry for a secondary battery, characterized by It contains solvents, negative electrode active materials, conductive agents, binders, thickeners, and additives, among which, The additive is any one or more of dimethyl sulfone, sulfolane, sulfolane, 3-methylsulfolane, and benzyl sulfone; The solvent is any one or more of deionized water, dimethyl sulfoxide, and N-methylpyrrolidone; The components in the negative electrode slurry, except for the solvent, are all solutes; by mass percentage, the solutes contain 92.0% to 95.0% of the negative electrode active material, 0.5% to 1.0% of the conductive agent, 1.0% to 1.5% of the thickener, 2.0% to 2.3% of the binder, and 0.2% to 1.5% of the additives.
2. The secondary battery negative electrode slurry according to claim 1, characterized by, It also meets at least one of the following conditions: The active material is selected from at least one of artificial graphite, natural graphite, mesophase carbon microspheres, silicon-carbon, silicon-oxygen, and hard carbon. The conductive agent is selected from at least one of carbon black, carbon nanotubes, graphene, and conductive fibers; The thickener is selected from at least one of sodium carboxymethyl cellulose and lithium carboxymethyl cellulose; The adhesive is selected from at least one of styrene-butadiene rubber and polyacrylic acid.
3. A method of preparing a negative electrode slurry for a secondary battery, characterized by, Includes the following steps: Provides a negative electrode base component, which includes a solvent, a negative electrode active material, a conductive agent, a binder, and a thickener; and The additives are mixed with the aforementioned negative electrode base components to obtain a secondary battery negative electrode slurry. The additive is any one or more of dimethyl sulfone, sulfolane, sulfolane, 3-methylsulfolane, and benzyl sulfone. The solvent is any one or more of deionized water, dimethyl sulfoxide, and N-methylpyrrolidone; The components in the negative electrode slurry, except for the solvent, are all solutes; by mass percentage, the solutes contain 92.0% to 95.0% of the negative electrode active material, 0.5% to 1.0% of the conductive agent, 1.0% to 1.5% of the thickener, 2.0% to 2.3% of the binder, and 0.2% to 1.5% of the additives.
4. The method of claim 3, wherein, The steps for providing the basic components of the negative electrode include: S1: Mix 43-47 parts of the negative electrode active material, 0.4-0.9 parts of the conductive agent and 0.2-0.5 parts of the thickener; S2: Add 29-32 parts of solvent to the mixture from step S1, mix, and then add 0.5-0.9 parts of thickener; S3: Add 18-20 parts of solvent to the mixing system of step S2, mix, and then add 0.4-0.8 parts of the binder to obtain the negative electrode basic components.
5. The method of claim 4, wherein, The method further includes the following steps: S4: Add 0.4-0.8 parts of the additive to the mixing system of step S3 to obtain the negative electrode slurry.
6. A secondary battery negative electrode sheet, characterized by include: Negative electrode current collector, A negative electrode film is disposed on at least one surface of the negative electrode current collector, the negative electrode film being formed from the secondary battery negative electrode slurry according to claim 1 or 2.
7. A secondary battery characterized by The secondary battery includes: a positive electrode, a negative electrode, a separator, an electrolyte, and a packaging film, wherein the negative electrode is the negative electrode as described in claim 6.
8. The use of a secondary battery in a new energy vehicle, characterized in that The secondary battery is the secondary battery as described in claim 7.